I've succeeded in all steps since i have access to a remote recovery system:
- dd yaifo.fs to /dev/hd1 and changed grub menu.lst
- access openbsd boot image through ssh with success
- installed openbsd to /dev/hd1 with success

however, after rebooting, i can't access openbsd anymore. very strange since It should have the same config as the boot image.

Any ideas are welcome...

Of course I can have a remote console connected to the server but that costs money

I'd do a standard installation of OpenBSD in a virtual machine under Ubuntu, attaching the second hard drive (/dev/hd1) to the VM.

Here's an example for Ubuntu, using qemu. Replace <whatever> with the raw device node for /dev/hd1. I don't use Linux often enough to know what that is:

# qemu -boot d -cdrom cd44.iso <whatever>

Let the standard install run, creating the MBR and installing the OS on the device. Then modify your GRUB configuration to allow a boot of the second hard drive. I can't guide you for that, as I don't speak Grubbish. If you let the install script "dedicate the drive to OpenBSD" the MBR will have a single active partition in the last slot (#3 if you use partitions 0-3, or #4 if you use partitions 1-4).

I can't tell anything about the reason for your hanging system. All I can tell is that appears to have entered multiuser mode, as you have messages that would come from rc(8), and that your network is misconfigured.

As I stated, I would install and configure a complete working system in a virtual machine.

More detailed information can be found in /var/run/dmesg.boot. See dmesg(8).